Physical disk space on storage devices, such as disk drives or disk arrays (grouped disk drives), is typically mapped to logical units of storage. Logical mapping can extend in many hierarchical levels. The smallest units can be grouped into logical volumes. Logical volumes can then be grouped further into volume groups, etc.
Application software references storage space on storage devices, such as disks drives and/or disk arrays, through these logical mappings. For high availability purposes, internal data mirroring software is typically used to create a duplicate copy of a volume group of a storage device, on a remote storage device such as a remote disk drive or disk array for example. The local volume and the remote volume pair is often referred to as a disk pair. A disk pair (which can include a pair of disk drives, a pair of disk arrays, etc.), or distinct grouping of disk pairs is typically known as a “resource”.
Array-based mirroring software provides functionality to create, split, delete, and check the status of a disk pair or resource. At the present time, however, an actual person or administrator must monitor the status of the disk pair based upon the information provided by the mirroring software, to perform maintenance tasks necessary to maintain a consistent disk pair state. This is because, as problems occur, the mirroring process may be suspended or stopped and the state of the disk pair or resource is no longer consistent between the two storage devices or disc arrays of the pair. The inconsistent state must be detected and the disk pair must eventually be resynchronized by the administrator in order to restore data consistency. At the present time, this detection and repair process is predominantly a manual process.
FIGS. 1a and 1b generally illustrate a basic disk mirroring configuration. Typically, a local host 2 instructs data storage on a local disk drive or drive array 6, also referred to as a local primary array or volume. During normal operation, data from the local primary volume 6 is mirrored or copied to the remote secondary volume on a remote disk drive or array 8 in a known manner, by way of a private link 10 connecting primary volume 6 with remote volume 8. The remote host 4 is in contact with the local host 2, and is also in contact with the remote volume 8.
As shown in FIG. 1b, however, problems typically occur when the private link 10 connecting volumes 6,8 is out for some reason, for example, or if the private link mirroring process is otherwise suspended or stopped for some reason as indicated by element 20 in FIG. 1b, for example. This results in an interruption of the mirroring process and may result in inconsistent data being stored on the volumes 6,8. Again, the suspension or stoppage of the mirroring process could occur for any number of reasons, such as that of a temporary outage in the private link of the volumes, for example. Since these private links often utilize leased telecommunication lines (e.g., asynchronous transfer mode (ATM); Dense Wave Division Multiplexing (DWDM); T3; etc.) that go through a shared wide area network (WAN) infrastructure, temporary outages are not uncommon.
When these outages occur, existing mirroring software can report the outage by reporting the state of the disk drive or disk array or disk array pair. For exemplary purposes only, five general reportable categories of disk pair states may be as follows:
Connected -the disk arrays of the disk pair are in a connectedstate. Changes to the local volume or local diskarray are being constantly sent to the remote ormirrored volume, or mirrored disk array.Resync -resynchronization is taking place (data is beingcopied out of order).Suspended -pairing (mirroring) has been suspended. As of themoment of this suspended operation, data in bothdisk arrays is the same. The disk pair could berestored to a connected state by resynchronizingthe data.Errorpairing or mirroring is suspended due to a permanentSuspended -error condition. Manual servicing by the administratoris typically done to return the disk pair to a knowngood state.Deleted -the disks are in a deleted mode (not mirrored orpaired).Traditionally, the administrator monitors the status of the disk pair as reported by the mirroring software; and thus the monitoring of disk pair status, the detection of any interruption in the mirroring process and repair thereof, are predominately manual processes.